1. Field of the Invention
The present invention relates to an oil pump of an automatic transmission.
2 Description of the Prior Art
Hitherto, various types of oil pumps for automatic transmissions have been proposed and put into practical use particularly in the field of motor vehicles. One of them is disclosed in a catalogue issued from ZAHNRADFABRIK FRIEDRICHSHAFEN AG OF WEST GERMANY. In the oil pump disclosed in this publication, a stator shaft of a torque converter extends through a casing of the oil pump from an outside (viz., the side where an oil pump gears are not provided) of the casing toward an inside (viz., the side where the oil pump gears are provided) of the same. The stator shaft has a portion splined with the oil pump casing, so that rotation of the stator shaft is suppressed.
However, due to its inherent construction, the above-mentioned oil pump has the following drawback. That is, when, for assembling the transmission, the stator shaft is thrust into the oil pump casing, it tends to occur that any burr produced by the splines is led into the gear chamber of the oil pump causing severe wearing and seizing of the gears. In fact, when the stator shaft is thrusted into the oil pump casing, a peripheral part of the opening of the casing may be shaved off by the splines of the stator shaft. Because the stator shaft is thrust into the oil pump casing from the outside toward the inside, the shavings thus produced by the splines are inevitably led into the oil pump gear chamber.